Many primate species, including humans, appear to be specialized for complex social behavior. Abundant behavioral evidence demonstrates that primates understand the consequences of their own behavior, to infer the likely behavior of other individuals, and to compute the balance of advantages and losses from potential social interactions. These computations are mediated by a specialized suite of visual and auditory communication signals. Such specialized signaling systems depend on specialized and dedicated neural circuitry. The long-term goal of this grant is to understand how social information from different sensory modalities is combined into a unified percept by the primate brain. Among human and nonhuman primates, faces and voices are the primary means of transmitting social signals. These visual and auditory signals can be integrated to enhance detection and discrimination. The major aim of this research, therefore, is to understand how dynamic facial expressions are integrated with vocal expressions in the auditory and multisensory regions of the cerebral cortex. By examining 1) the temporal relationships between auditory and visual signals, 2) the role of facial movement, and 3) the ability of primates to use these signals to make sophisticated judgments about the physical characteristics of social group members, we hope to uncover principles of visual-auditory neuronal interactions related to social cognition in the temporal lobe. Despite the fact that dysfunction of homologous systems in humans probably contributes to a variety of debilitating mental disorders, these mechanisms remain relatively unexplored by neurobiologists. Thus, the goals of this research have direct relevance to communication disorders in general and autism in particular. The hallmark of autism is an inability to behave in a socially-appropriate manner. Autistics are "mind blind"-they do not process the relevant sensory cues necessary for normal social interactions with other individuals. In part at least, this deficit is likely due to the autistics'specific impairment in face and voice processing, but not in other domains of visual and auditory function.